This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to a Japanese Patent Application 2002-054040, filed on Feb. 28, 2002, the entire content of which is incorporated herein by reference.
This invention generally relates to a variable valve timing device for controlling opening and closing timing of intake and exhaust valves of an internal combustion engine.
A known variable valve timing device has been disclosed in a Japanese Patent Laid-Open published as No. 1999(H11)-132014. The disclosed variable valve timing device includes a rotation transmitting member rotatable integrally with one of a rotation shaft of an engine and an intake and exhaust valves controlling member, which is capable of controlling an opening and closing of the intake and exhaust valves of the engine. The disclosed variable valve timing device further includes a rotor member disposed in the rotation transmitting member so as to be rotated relative to the rotation transmitting member and rotatable integrally with the other of the rotation shaft of the engine and the intake and exhaust valves controlling member. A fluid chamber is defined between the rotor member and the rotation transmitting member. A vane is radially equipped to either the rotor member or the rotation transmitting member so as to divide the fluid chamber into an advanced angle chamber and a retarded angle chamber. A covering member is fixed to the rotation transmitting member so as to cover the fluid chamber. A biasing member, for example a torsion coil spring, is disposed between the closing member and the rotor member so as to bias the rotor member in a rotative direction. In this known variable valve timing device with the above-described structure, each of the covering member and the rotor member is provided with a groove which houses an edge portion of the biasing member and possesses a spiral shaped structure.
According to the above-disclosed variable valve timing device, each groove of the covering member and the rotor member comes in contact with an entire rolled edge surface of the biasing member. Accordingly, a contact resistance between the biasing member and each groove is relatively large when the rotor member is rotated relative to the rotation transmitting member. In this case, the rotating performance of the rotor member relative to the rotation transmitting member may be deteriorated, thereby affecting on operation of the variable valve timing device.
The present invention therefore seeks to provide an improved variable valve timing device in which a relative rotation of a rotor member and a rotation transmitting member may be smoothly performed as being intended, thereby the performance of the variable valve timing device can be improved.
According to an aspect of the present invention, a variable valve timing device includes a rotation transmitting member rotated integrally with one of a rotation shaft of an engine and an intake and exhaust valves controlling member for controlling an opening and closing of intake and exhaust valves of the engine, and a rotor member disposed in the rotation transmitting member to be rotated relative to the rotation transmitting member and rotated integrally with the other of the rotation shaft of the engine and the intake and exhaust valves controlling member, a fluid chamber defined between the rotor member and the rotation transmitting member, a vane radially equipped to one of the rotor member and the rotation transmitting member so as to divide the fluid chamber into an advanced angle chamber and a retarded angle chamber, a covering member fixed to the rotation transmitting member for covering the fluid chamber, and a biasing member disposed between the covering member and the rotor member for biasing the rotor member in a rotative direction thereof. An axial edge surface of the biasing member discontinuously comes in contact with at least one of the rotor member and the covering member.
At least the one of the rotor member and the covering member includes a recessed portion for housing an axial edge portion of the biasing member. The recessed portion possesses a discontinuous surface at a bottom thereof.
The biasing member is a torsion spring of which one end is engaged to the covering member and other end is engaged to the rotor member. The recessed portion for housing the axial edge portion of the torsion spring is a groove with a substantially helical shaped structure. The discontinuous surface is provided at a bottom of the groove with the substantially helical shaped structure.